Rafael Nadal will return to No.1 in the world rankings for the first time since July 2011, after his semi-final opponent Tomas Berdych retired injured on Saturday at the China Open.

Nadal only needed to make the final in Beijing to edge ahead of Novak Djokovic in the new rankings, which will be announced on Monday.

The Spaniard was a break up at 4-2 in the opening set when Czech Berdych retired soon after taking an injury timeout.

Nadal has enjoyed a remarkable season, returning from injury to dominate the hardcourt tournaments with a win-loss record of 27-0.

Djokovic, who has topped the rankings for 101 weeks, plays Richard Gasquet of France in the other semi-final later on Saturday.

Nadal, sidelined for the second half of last year with a knee injury, has finished the season as No.1 twice before, in 2008 and 2010, and is unbeaten since crashing out of Wimbledon in the first round in June.

The 27-year-old, tipped to eclipse Roger Federer’s record of 17 grand slam titles, has won 10 ATP World Tour titles in 2013.

In the women’s semis, top-ranked Serena Williams will play Agnieszka Radwanska of Poland and Petra Kvitova of the Czech Republic takes on Serbia’s Jelena Jankovic.